The invention relates to intersomatic spine implants.
Document FR-2 727 003 discloses an intersomatic spine implant for putting into the place of a vertebral disk after it has been removed, and comprising a body having two plane faces that come into contact with the adjacent vertebral bodies. It has two housings for receiving anchoring screws, disposed in such a manner that the screws project from respective contact faces so as to be anchored into the adjacent vertebral bodies. Each screw slopes relative to the associated contact face because the head of the screw projects from a side of the body so as to be capable of being driven once the implant has been received between the vertebral bodies. Nevertheless, it is difficult to put the screws into place because of the slope of their axes. Furthermore, the positioning of the screws cannot be improved in order to optimize the quality of the anchoring they provide without making them less accessible.
U.S. Pat. No. 5,702,391 discloses an intersomatic implant comprising a body, slidably movable pins in the body for projecting from outside faces of the body, and spherical cams slidably movable in an axial duct of the body. An actuator piece disposed at the mouth of the duct enables thrust to be applied to the cams which move the pins by a ramp effect so that they project and thus anchor the implant in the plates of the associated vertebrae. Such an implant makes it much easier to achieve robust anchoring between the vertebrae. However, the implant is very difficult to remove should that be necessary, which in contrast is not the case with the implant disclosed in above-mentioned FR-2 727 003 since it needs only to have the screws undone to eliminate anchoring between the implant and the plates.
An object of the invention is to provide an implant that is easy to install and remove.
To achieve this object, the invention provides an intersomatic spine implant comprising a body, at least one anchoring element movable relative to the body to project from a contact face of the body making contact with a vertebra, and at least one cam slidable relative to the body and suitable for displacing the anchoring element relative to the body by the effect of a ramp engaging the anchoring element, wherein the cam and the anchoring element are arranged so that the cam moves the anchoring element in two opposite displacement directions.
Thus, the anchoring element is moved by means of the cam, by taking action on the cam. Since action is no longer taken directly on the anchoring element, constraints associated with accessibility of the anchoring element are to a very large extent eliminated. As a result, the anchoring element is easier to drive into place during surgery. Furthermore, since it is no longer necessary to make the anchoring element directly accessible, its positioning can be modified in a very wide variety of ways so as to ensure that it performs its anchoring function as well as possible. Consequently, the operation of installing the anchoring element is made easier, while also making it possible to improve the quality of anchoring.
In addition, since the action of the cam is reversible, it enables the or each anchor element to be actuated so as to go from the extended position to the retracted position. It is then easy to remove the implant. This action of the cam on the anchoring element is positive in the sense that the cam entrains the anchoring element. The action of the cam does not consist solely in leaving the way open for the implant to be capable of penetrating into the body under the effect of external pressure exerted on the anchoring element by the material of the vertebrae. Thus, in particular, it is possible to remove the implant a long time after it has been put into place.
The implant of the invention may also present one or more of the following characteristics:
the cam has a thread suitable for co-operating by screw engagement with an actuator for driving the cam from outside the body;
the actuator is suitable for being mounted to move
in rotation relative to the body;
the cam is mounted to move sliding relative to the body;
the cam has an end providing a face that is undercut relative to a travel direction of the cam so as to enable the cam to be extracted from the body;
the implant includes at least two anchoring elements and at least two cams suitable for moving respective anchoring elements;
the two cams are arranged so that their threads cooperate with a common actuator;
the anchoring element slopes relative to a general plane of the contact face;
the implant includes at least two anchoring elements suitable for projecting from the same contact face;
the implant includes at least four anchoring elements suitable for projecting from the same contact face and disposed in two rows defining mutually-parallel alignment directions;
the body has two contact faces for making contact with respective vertebrae and at least one recess extending between the contact faces;
the portion of the anchoring element suitable for projecting from the contact face has faces that are undercut relative to the sliding direction of the element towards the vertebra; and
the implant presents at least two anchoring elements and an element-carrier rigidly connected to the anchoring elements.